In high quality medical radiology, it has always been desirous to measure the kVp (high voltage peak waveform) supplied to an x-ray generator in order to properly maintain an x-ray machine in precise calibration. Inaccurate calibration of an x-ray generator can result in poor radiographs, shortened component life, and possible violation of the Radiation Control Act. Because the voltages which are fed by a pair of cables to the x-ray generator in the diagnostic mode range from thirty to seventy-five kVp per cable for a total of sixty to a hundred fifty kVp, it is undesirable to make a direct measurement of such high voltage. This is especially the case for persons unskilled in the art of handling such high voltage apparatus.
One prior art device which has attempted to provide a means for calibrating an x-ray machine includes a high voltage divider having two large resistance sections which are connected between the anode of the x-ray generator and ground and between the cathode of the generator and ground. Although the high voltage divider provides a satisfactory measuring circuit, such a device can only be utilized by qualified personnel.
Another attempt to provide a means for calibrating radiographic equipment consists of a step wedge penetrometer. The penetrometer is constructed of a metal such as copper or aluminum and includes a series of steps each having an increased thickness to provide greater attenuation of the x-ray beam. In operation, the step wedge penetrometer is placed on a detector such as standard x-ray film and exposed to the x-ray beam. The film is then compared to another exposure made without the use of the penetrometer but using a detector of lower sensitivity. The lower sensitivity detector can either be another x-ray film of reduced sensitivity, or the same type of film used with the penetrometer, but fed through an attenuator. The density of the step wedge image is related to the effective kVp of the x-ray beam. While such a measurement technique is effective and successful, making a succession of exposures to completely calibrate a system is a laborious and time consuming task.